1. Field of the Invention
The present invention relates to an image forming optical system, and image pickup apparatus using the same, and information processing apparatus.
2. Description of the Related Art
In recent years, with the thinning of equipment's such a mobile telephone, a portable terminal, and a notebook-size personal computer, a camera module in which, a length of an optical system in an optical axial direction is thinned to the minimum has been sought. Moreover, with the technological development of an image pickup element and the increasing needs of the market, it has been sought that an image pickup element with a large number of pixels is used, and that an image pickup lens has a high resolution.
In order to fulfill the requirement, a large number of optical systems with a single focal length, which include four aspheric lenses, have been proposed.
As an optical system in which, the number of lenses is let to be four, and shortening of an overall length of the optical system and widening of an angle of field have been facilitated while improving an imaging performance, U.S. Pat. No. 7,777,972 Specification, and Japanese Patent Application Laid-open Publication No. 2010-060835 have been proposed. Optical system in the abovementioned patent literatures includes four aspheric lenses, and has an improved performance.